Fig. 2. Effect of Ca²⁺ and calmodulin on the myosin 1c-PHR1 interaction. (A) Effect of the Ca²⁺ concentration. Myosin 1c IQ₄ tail or GST alone was incubated with [³⁵S]PHR1b in the presence of 100 µM EGTA or 50 µM Ca²⁺. PHR1b interacts with the tail of myosin 1c in both cases (upper panel). In the reciprocal experiment, full-length myosin 1c binds to GST-PHR1b in the presence of 100 µM EGTA or 50 µM Ca²⁺ (lower panel). (B) Effect calmodulin (CaM). GST-PHR1b binds to ³⁵S-labelled full-length myosin 1c in the absence (–) or presence of calmodulin (1.5, 7.5 or 15 µM) (upper panel). In the reciprocal experiment, GST-myo1c T701 or GST was incubated with ³⁵S-PHR1b in the absence or presence of calmodulin (1.5, 7.5 or 15 µM). The myosin 1c IQ₄ tail-PHR1b interaction is not affected by any of the calmodulin concentrations tested (lower panel). Positions of molecular mass markers are indicated in kDa on the right-hand side of blots.